ABSTRACT
In this chapter, I review some of the empirical evidence collected from a comprehensive educational intervention research synthesis for students with learning disabilities (Swanson, Hoskyn, Lee, & O’Shaughnessy, 1997). The synthesis used meta-analytic techniques to aggregate the research literature on intervention. Meta-analysis is a statistical reviewing technique that provides a quantitative summary of findings across an entire body of research (Cooper & Hedges, 1994; Hedges & Olkin, 1985). The results of individual studies are converted to a standardized metric or effect size. These scores are then aggregated across the sample of studies to yield an overall estimate of effect size. Particular attention is given to the magnitude of the effect size estimate. According to Cohen (1988), .80 is considered a “large” effect size estimate, .50 a moderate estimate, and .20 a small estimate.
